Leukocyte capillary agglutination (CA) is a new serologic test for the detection of human anti-leukocyte antibodies. It has been demonstrated that this is a very sensitive, reliable, and unique technique that detects a broad range of specificities including cytotoxic, agglutinating, HL-A specifically anti-neutrophil, and probably others that are not recognized by existing standard methods. Data has been accumulated that some of the specificities detected by CA may be important with regard to human kidney, cardiac, and in certain severe transfusion reactions. The exact nature of these specificities is unknown and antisera to systematically detect them are not yet available. The purposes of the proposed investigation include: 1) to identify new leukocyte antisera with particular reference of non-HL-A specificities detected by capillary agglutination as they are found in the sera of pregnant women, post multiple transfused recipients, and by protocol immunization. 2) To analyze these antisera against panels of normal cells to obtain group correlation and soecificity by absorption techniques, by calculation of correlation coefficients, and by comparative analysis utilizing 2 X 2 Chi-square statistical data. 3) To investigate these sera and others that have been shown to contain non-HL-A antibodies in transplanted and non-transplanted sibs paired for HL-A compatibility, in other kidney graft recipients that have been transplanted with parent to sib or sib organs, and in unrelated graft pairs. Pre- and post-transplant serum will also be examined for the presence of non-HL-A antibodies directed against donor tissues and against a panel of normal cells. Febrile transfusion reactions will be investigated as well. 4) Ultimately, prospective typing with the panel of sera will be utilized in controlled studies to determine whether they function as histocompatibility antigens in kidney, bone marrow and skin transplantation.